This invention essentially relates to compositions with improved urease-inhibiting effect comprising (thio)phosphoric acid triamide and further compounds and the use of such compositions as additive or coating material for nitrogen-containing fertilizers.
Worldwide, the predominant and further-increasing amount of the nitrogen used for fertilizing is employed in the form of urea or urea-containing fertilizers. Urea itself, however, is a form of nitrogen which is absorbed very little if at all, being hydrolyzed relatively rapidly by the enzyme urease, which is present ubiquitously in the soil, to form ammonia and carbon dioxide. In this process, in certain circumstances, gaseous ammonia is emitted to the atmosphere, and is then no longer available in the soil for the plants, thereby lowering the efficiency of fertilization.
It is known that the degree of utilization of the nitrogen when using urea-containing fertilizers can be improved by spreading urea-containing fertilizers together with substances which are able to inhibit or decrease the enzymatic cleavage of urea (for a general review, see Kiss, S. Simihäian, M. (2002) Improving Efficiency of Urea Fertilizers by Inhibition of Soil Urease Activity, ISBN 1-4020-0493-1, Kluwer Academic Publishers, Dordrecht, The Netherlands). Among the most potent known urease inhibitors are N-alkylthiophosphoric acid triamides and N-alkylphosphoric acid triamides, which are described in EP 0 119 487, for example.
Additionally, mixtures of N-alkylthiophosphoric acid triamides such as N-(n-butyl)thiophosphoric acid triamide (NBPT) and N-(n-propyl)thiophosphoric acid triamide (NPPT) can be used. The mixtures and their preparation are described in US 2010/218575 A1, for example.
These urease inhibitors are described in U.S. Pat. No. 4,530,714, for example. In order for this class of compound to be able to act as a urease inhibitor, there must first be a conversion to the corresponding oxo form. That form reacts subsequently with the urease, causing its inhibition.
It is advisable to apply the urease inhibitors together with the urea onto or into the soil, since this ensures that the inhibitor comes into contact, together with the fertilizer, with the soil. The urease inhibitor may be incorporated in the urea by, for example, dissolving it into the melt prior to urea granulation or prilling. A process of this kind is described in U.S. Pat. No. 5,352,265, for example. A further option is to apply the urease inhibitor to the urea granules or prills, in the form of a solution, for example.
Corresponding processes for application, and suitable solvents, are described in US 2010/218575 A1, for example. Other suitable additives, for example amines selected from methyldiethanolamine, tetrahydroxypropylethylenediamine, trimethylaminoethylethanolamine, N,N,N′,N′-tetramethyl-1,6-hexanediamine, N,N′,N″-tris(dimethylaminopropyl)hexahydrotriazine, and 2,2′-dimorpholinyldiethyl ether, are described in US 2011/0154874 A1.
The storage life of the urease inhibitor is limited. The higher the temperature, the shorter the storage life. If, for example, urea is stored under tropical conditions, a major part of the urease inhibitor has undergone decomposition, generally, after about four weeks of storage. If the urease inhibitor is introduced into the urea melt, the decomposition is less. For the commercialization of the urea stabilized with the urease inhibitor, however, it is often vital to apply the urease inhibitor to urea and to store the treated fertilizer until the time of its spreading to the soil.
One of the objects of the present invention was to provide a composition containing (thio)phosphoric acid triamide which                (i) enhances the stability of the (thio)phosphoric acid triamide(s), and/or        (ii) enhances the urease inhibiting effect of the (thio)phosphoric acid triamide(s), and/or        (iii) enhances the yield increase effect of the (thio)phosphoric acid triamide(s), and/or        (iv) has a relatively long storage life, particularly before being applied to or coated on nitrogen-containing fertilizers, and/or        (v) enhances the stability of the (thio)phosphoric acid triamide particularly when applied to or coated on nitrogen-containing fertilizers such as urea, and/or        (vi) protects the (thio)phosphoric acid triamide applied to or coated on nitrogen-containing fertilizers such as urea from decomposition or loss, and/or        (vii) is toxicologically unobjectionable, and/or        (viii) does not adversely affect the urease-inhibiting effect and/or activity of the (thio)phosphoric acid triamide, and/or        (ix) can be easily and safely packaged, transported and shipped, even in large quantities, and/or        (x) can be easily and safely handled and applied for soil treatment, even in large quantities, and/or        (xi) can be easily recognized and distinguished in case several different compositions are used for different purposes.        